The invention relates to a roll of material also called xe2x80x9cribbon rollxe2x80x9d and supporting a thermoplastic ribbon of shallow cross-section and generally cross-wound on a hollow core, the ribbon being used for strapping.
Rolls of material in the form of lengths of string, bands, ribbons or the like that are made of textile fiber materials, mono-filaments or the like generally comprise a dimensionally stable hollow core and optionally a sleeve or a cuff circumferentially surrounding the outside of the fully wound material.
As regards conventional ribbon rolls, the hollow core consists of a cardboard tube made comparatively thick to assure stability, in particular also against the radial forces exerted by the wound material. Ordinarily the hollow core-side end of the material to be wound on the hollow core is affixed by an adhesive strip to the hollow core, ie to its surface.
Cardboard hollow cores offer the advantage of being fairly economical. On the other hand they incur the drawback of being relatively heavy and foremost that they are significantly bulky, and consequently they entail some cost in shipping and storage. Another and significant drawback concerns their waste disposal becausexe2x80x94as a rulexe2x80x94they will be wound with a useless remnant of material. Homogeneous recycling therefore requires to remove the material residues from the cardboard and to dispose separately of the two wastes.
As a rule thermoplastic strapping ribbons are made of polypropylene (PP) or of polyethylene (PE) which are both plastics of which the waste disposal is comparatively problem-free. Regarding the problem of waste disposal, the German patent document U1 93 15 668 appropriately proposes that the roll of material be fitted with a hollow core (therein called inner muff) made of a strip of plastic, in particular PP. The thickness of this plastic sheet is preferably 0.5 to 1 mm, especially 0.7 mm approximately. The hollow core consists of a rigid-flexible strip of such a material with specially shaped end segments allowing to insert one strip end in the form of a tab at the other end of the cut-to-size piece into a slotted aperture in such manner that the cut ends of the cylindrical inner cylinder and so affixed to each other are fixed in place.
This design of the inner hollow core made of a rigid-flexible strip of plastic requires machine processing especially as regards the shaping of the strip ends. Moreover skilled handling is required to form the muff from the plastic strip. The shipping and storage of the inner muff in the form of a plastic strip as yet not transformed into a hollow core indeed have been improved relative to the initially cited state of the art, but even in this technology prefabrication and special storage are expensive.
Based on the above state of the art, the object of the present invention is essentially to propose a substantially simplified roll of material relative to the state of the art.
The invention solves this problem by providing a plastic strip including an adhesive-coated sheet of which the adhesive fitted surface forms the outside of the hollow core facing the material.
In the first place it is essential for the invention that it distance itself from the heretofore basic concept that the hollow core must be very rigid as a tubular body, for instance like a cardboard shell, or, as regards the inner hollow core of the German patent document U1 93 15 668, that it must be a rigid/flexible structure. Instead the invention is based on the insight that the wound material per se can impart high dimensional strength to the entire roll of material, especially when the surface of the material facing the hollow core is firmly bonded by its first winding layer to this hollow core. Using this insight, the invention in surprising manner manages to make the hollow core from an adhesive coated sheet of a thermoplastic such as polypropylene (PP) or polyethylene (PE), the sheet constituting the hollow core being only 20-30xcexc thick. In this manner it is possible in simple manner to use the same plastic both for the sheet and for the material to be wound on it, thereby assuring waste disposal of homogeneous materials in absolutely reliable manner. On the other hand a commercial pressure-sensitive adhesive film can be used as the sheet forming the hollow core. Illustratively a pressure sensitive film such as is used for packing tape may be used.
In this respect the invention is characterized by unusual simplicity of configuration, in particular as regards the hollow core.
Furthermore in case the said material is a conventional thermoplastic ribbon for strapping tools, the invention exploits the very nature of the ribbon of which the surface is usually made salient for reasons of strength. The surfaces of the individual wound layers of the ribbon roll therefore lie frictionally against each other and the finished roll will not fall apart even when being moved/shipped horizontally. Again the invention offers in this respect further strengthening by means of a sheet fitted on its side facing the material with an adhesive-coated plastic foil fitted with a projecting, adhesive-free or adhesive-neutralized tear-open tab external to and taut around the material like a sleeve.
Accordingly the invention concerns a simple method to produce a roll of material of the cited kind. This method is characterized by the following steps:
(a) To form the hollow core of the roll of material, an adhesive-coated strip of foil is wound by its surface opposite the adhesive-coated outer surface around a substantially circular-cylindrical support mandril,
(b) By bonding overlapping sheet segments (overlap zone) the strip of foil is affixed on the support mandril,
(c) The beginning of the material to be wound is attached to the adhesive-coated outer surface of the hollow core,
(d) The support mandril is set in rotation about its longitudinal axis until the roll of material has reached the desired quantity of material, and
(e) The roll of material is removed from the support mandril, and optionally another step (f) may be carried out before or after step (e), namely
(f) An adhesive pressure-sensitive plastic foil is deposited on the outside of the roll of material to act as a circumferential, taut sleeve.
Lastly the invention proposes a device with which to carry out the above method and is characterized in that this device includes a support mandril in the form of an expansion mandril composed of segments which are substantially adjustable radially to axis of rotation and which following preparation of the roll of material can be retracted to decrease the mandril diameter to allow withdrawing the roll of material from the expansion mandril.
When winding the material the handling of the hollow core merely requires the simple expansion mandril. When processing the roll of material, that is supporting it when the material is being used up, no other special devices are used. The conventional winding mandrils or support rollers can be used by means of which heretofore the conventional rolls of material for instance of cardboard were processed into hollow cores.